Atmospheric Pressure Photoionization (APPI) Theory

Atmospheric pressure photoionization (APPI) is a complement to ESI and APCI and has been developed to broaden the range of ionizable analytes at atmospheric pressure. APPI is important in the analysis of certain compounds that are not easily ionizable by ESI or APCI like low-polarity and non-polar compounds. In APPI, the ionization process is accomplished by exposing an aerosol of droplets to photoirradiation. A molecular radical ion is formed when the molecule absorbs a photon. This module will discuss the theories of the ion production process in APPI.

Topics include:

• APPI introduction
• APPI instrumentation
• Suitable samples for APPI
• APPI interfacing details
• APPI eluent flow rates
• APPI dual mode of operation
• APPI ionization mechanisms
• APPI positive ion mode
• APPI negative ion mode